I took part in a workshop looking at the potential for deep geothermal energy in Scotland at the British Geological Survey (BGS) in Edinburgh.
The workshop related to a study being carried out by AECOM and the BGS for the Scottish Government. Topics covered included the resource, finance, legal and licensing issues, and planning and the environment. Lots of interesting discussion follows, but here I’ll just stick to a few observations about the resource, and how it might be used.
Looking at the resource, the BGS outlined how the latest thinking suggests that the temperature gradients at depth (say 2km to 5km or so) – and therefore the deep geothermal resource – might previously have been underestimated. However, there are no on-shore boreholes of sufficient depth in Scotland to definitively prove the case either way. The vision is that temperatures of 150ºC or so could be tapped into, and the energy used to generate electricity. A distinct advantage of this form of renewable power over others is that it can be run as baseload, and turned down as required: generation would not be at the whim of a fluctuating resource. There was a call for this to be recognised in the ROC regime for geothermal energy.
More accessible, though, is the not-so-deep geothermal energy that might be tapped into through the extensive redundant mine workings throughout the Central Belt. Existing at depths from near the surface down to around 900m at some mines, huge volumes of water (temperatures from around 12 ºC up to around the mid-thirties) can be abstracted at depth, passed through a heat pump, and returned – cooler – to a point nearer the surface. There are already a couple of fairly shallow schemes using mine water in Scotland, but the prospect of accessing the much warmer water at depth attracted much interest. The heat extracted can be used to heat people’s homes, and it was noted that there is a correlation between the availability of this resource and fuel poverty in former mining communities, so the time may well have come for such developments.
The BGS has already done a lot of work in 3D mapping of mine-workings in Scotland. Its 3D subsurface geological model of the Clyde Gateway, Glasgow can be seen here:
Related press article here: http://www.guardian.co.uk/science/2012/sep/07/flooded-mines-glasgow-heating-needs